LOS ANGELES — Shirley Robin has begun noticing some changes in her brain power recently. "I'm forgetting things very easily," she says. "I'm repeating stories all the time. There's no question that there's a loss of memory here."

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During a recent afternoon at UCLA, she and about a dozen other seniors took part in a class aimed at enhancing their cognitive abilities. Through a series of "mental aerobics" activities, the class participants learned memory strategies and exercises to help keep their minds in shape.

One exercise focused on remembering people’s names. The instructors told the class to zero in on some aspect of a person’s face and try to associate it with something they’d remember. For instance, Freddie Katz has large green eyes like a cat.

Other activities centered on figures. When trying to remember a number such as 37, the instructors advised, make a story out of it: The triplets drank 7 UP. For the address of 76 Willow Avenue, think of 76 trombones in a willow tree.

In addition to such brain-training classes that are now offered in some cities, various books, videos and web sites are devoted to helping people boost their memory. And early next year, chapters of the Alzheimer’s Association are planning to offer “Maintain Your Brain” workshops to educate people about lifestyle measures -- including mental and physical activity -- to help preserve their cognition.

Experts say programs aimed at boosting brain power are attractive to many aging baby boomers and older people who are worried about developing Alzheimer’s and other forms of dementia. There's reason for concern: Alzheimer's cases are expected to soar in the coming decades as the population ages. But there is some good news too: Increasing evidence suggests there are steps we can take to help keep our brains in shape.

'Use it or lose it'Until about 25 years ago, most scientists believed that senility was an inevitable part of aging, according to Dr. Gary Small, director of the UCLA Center on Aging who launched the memory training classes on campus.

But they now know that’s not necessarily the case, says Small, author of “The Memory Prescription.”

Research has demonstrated, for example, that higher levels of education and plenty of mental stimulation throughout life are associated with lower rates of Alzheimer’s, he notes.

A study published last year in The New England Journal of Medicine found that people over 75 who often read, danced and played board games or musical instruments had lower rates of dementia, including Alzheimer's, than those who didn't frequently engage in such stimulating pursuits.

“It’s the use-it-or-lose-it theory,” Small says. “If you keep your brain cells active it improves their efficiency. You develop what we believe is a cognitive reserve.”

How much is enough?
So how much do you need to do now to keep your brain functioning well into old age? It’s not entirely clear but experts say it all adds up -- and it’s never too late to start.

Even people who are at high risk of Alzheimer’s because of a family history of the disease may see benefit. They may not completely steer clear of the disease, but they may reduce or delay its symptoms for months or even years, according to Small and others.

That’s the message the Alzheimer’s Association is hoping to get out with its new campaign, says Dr. Bill Thies, the group's vice president for medical and scientific affairs.

Staying mentally active -- be it through working crossword puzzles, reading, taking college courses, learning a new language, playing games or going to the theater -- is “the prudent thing to do” as we age, says Thies. “But it doesn’t come with a guarantee card, unfortunately.”

The same goes for physical activity, according to Thies. Researchers know that people who exercise regularly have healthier brains and less Alzheimer’s than their couch-potato counterparts, though they don’t know exactly how much or what specific kinds of exercise offer the most protection.

Laura Kleinhenz for MSNBC.com

It's never too late to learn for Sandy Baron, 86, left, and Shirley Robin, 75, who work on a memory exercise during a class at UCLA.

Research published in September in the Journal of the American Medical Association found that even walking appears to have a significant benefit. A study of men ages 71 to 93 showed that those who walked less than a quarter of a mile a day were nearly twice as likely to develop Alzheimer's disease or other forms of dementia as those who walked more than two miles daily. And a second study of women ages 70 to 81 found that women who walked just one-and-a-half hours a week performed better on cognitive tests than those who were more sedentary.

Until more definitive studies are done, Thies recommends sticking with the current public-health recommendation to get 30 minutes of moderate exercise, such as walking or biking, most days of the week.

Staying connected
Such activity keeps arteries fit and can promote healthy blood flow to the brain, he says, and there’s some evidence it may even cause the release of nerve growth factors that create new connections in the brain.

Exercise also appears to help by regulating blood sugar, which seems to play a key role in brain health, according to Dr. Antonio Convit, medical director of the Center for Brain Health at New York University.

In a study published last year in the Proceedings of the National Academy of Sciences, Convit and his colleagues found that people with impaired glucose tolerance performed worse on memory tests than people with normal blood-sugar control. What’s more, those with impaired glucose tolerance actually had brain shrinkage in an area involved in memory.

Glucose fuels the brain, Convit explains, so when it’s in short supply there’s trouble.

Experts say people like Robin who are hoping to keep their brains in shape as they age should follow the same advice that goes for keeping the rest of their bodies fit: Find exercises that you enjoy and are likely to stick with over the long-term. When it comes to working out the brain, though, activities should be both physical and mental.

Memory programs that give specific instructions about exercises to follow are fine, Thies says, but you don’t really have to over-think this one too much.

“The advice is fairly simple,” he says. “Moving is better than sitting and staying engaged is important.”